Raman spectrometry, which identifies and detects substances included in samples by applying the Raman effect, is conventionally known. The Raman effect is a phenomenon in which light having a wavelength different from that of incident light is scattered when the incident light is caused to enter a substance. The difference in energy, that is, the difference in wavelengths, between the scattered light (Raman scattered light) and the incident light corresponds to the molecular structure or the crystal structure of the substance. Raman spectrometry utilizes this phenomenon, by irradiating a light beam having a single wavelength onto a sample, spectrally detecting Raman scattered light generated thereby, and identifying specific substances.
Recently, surface enhanced Raman spectrometry (SERS: Surface Enhanced Raman Scattering), which is capable of significantly amplifying Raman scattered light and detects the amplified Raman scattered light, has been proposed and is being widely researched. Surface enhanced Raman spectrometry utilizes the fact that the intensity of Raman scattered light is amplified when light is irradiated onto a substance which is in contact with a metal member having fine protrusions and recesses on the surface thereof, and enables detection of extremely small amounts of substances. PCT Japanese Publication No. 2006-514286, Japanese Unexamined Patent Publication No. 2008-164584, and S. Ghadarghadr et al., “Plasmonic array nanoantennas on layered substrates: modeling and radiation characteristics”, OPTICS EXPRESS, Vol. 17, No. 21, p. 18556, 2009 disclose examples of apparatuses for performing surface enhanced Raman spectrometry.